Allen-Bradley (Rockwell Automation) parts are identified by a catalog number that starts with a bulletin number - the leading digits that tell you which product family the part belongs to. Recognizing the bulletin is the fastest way to know what you're looking at and to source the right replacement, especially for the older lines that are now hard to find.
The bulletin number tells you the platform
For PLCs and I/O, the leading number maps to a controller family:
- 1756 - ControlLogix (large, rack-based, high performance).
- 1769 - CompactLogix / Compact I/O (mid-range).
- 1768 - CompactLogix (earlier generation).
- 1734 - POINT I/O (distributed, modular).
- 1794 - FLEX I/O (distributed).
- 1746 / 1747 - SLC 500 (legacy; 1746 = I/O and chassis, 1747 = processors).
- 1761 / 1762 / 1763 / 1764 / 1766 - MicroLogix small controllers (1000/1100/1200/1400/1500).
- 1785 - PLC-5 (legacy).
- 2080 - Micro800 (Micro820/830/850/870).
Other common bulletins you'll see
- 20 / 22 / 25 - PowerFlex variable-frequency drives (e.g. 20A, 22B, 25B).
- 800 - push buttons, pilot lights and operator devices.
- 100 / 700 - contactors and control relays.
- 140 - motor protection circuit breakers and overloads.
- 1606 / 1609 - power supplies and UPS.
- 2711 - PanelView HMI / operator terminals.
Reading the rest of the number
After the bulletin, a series of letters and digits describes the specific module, rating, I/O count and series/revision. For example, in 1756-L71 the 1756 is ControlLogix and L71 identifies a specific Logix controller; in 1769-IF8 the 1769 is Compact I/O and IF8 is an 8-channel analog input module. Series letters (A, B, C) at the end indicate hardware revisions that can matter for firmware compatibility, so quote the full catalog number including the series.
Verify before you buy
Bulletin recognition gets you to the right family fast, but always confirm the complete catalog number - and its lifecycle status - against Rockwell's official product directory before purchasing, since many SLC 500, PLC-5 and early MicroLogix parts are now discontinued.
We source Allen-Bradley parts - including obsolete lines
Send us the full Allen-Bradley catalog number you need and we'll identify it and respond within two business days, with price and lead time where we have them and a full quote once our suppliers confirm. Discontinued ControlLogix, SLC 500 and PLC-5 modules are exactly the kind of thing we source. We are an independent reseller and not affiliated with Rockwell Automation; the Allen-Bradley name is used here for identification only.